1. Field of the Invention
This invention relates generally to powered surgical cutting devices. More particularly, this invention relates to powered surgical blades and means for joining these blades to a surgical handpiece. Still more particularly, this invention relates to a powered sternum saw provided with a guard and a safety interlock to prevent operation of the saw unless all parts are properly assembled.
2. Description of the Prior Art
Surgical saws are well known for cutting various types of tissue during surgical procedures. The saws are often provided with shields or guards to prevent inadvertent damage to tissue adjacent the surgical work site. Such guards are particularly important when using powered surgical saws.
One type of known surgical cutting device is a sternum saw which is, as the name implies, used for cutting through the sternum during a surgical procedure. A collet mechanism is provided to secure the reciprocating saw blade to the handpiece and the collet nut is tightened with a wrench or other tool in order to hold the flat "saber saw" in a longitudinally reciprocating drive shaft. The collet not only grips the saw blade but also acts to squeeze a locking alignment ball into a hole formed in the proximal end of the blade in order to prevent the blade from falling out of the handpiece should the collet become loose. Because of the sensitive location of the sternum such surgical saws are generally provided with a saw blade guard in order to partially enclose the reciprocating saw blade to preclude it from accidentally cutting unintended tissue. However, the presence of the guard limits access to the collet nut and makes it more difficult to tighten the blade. Additionally, the need to keep track of a separate tool or wrench to tighten the collet adds to the difficulty. Improvements in design are desirable to facilitate the assembly of the blade onto the handpiece. In addition to facilitating attachment of the saw blade to the handpiece, it is always desirable to incorporate additional safety features in powered surgical saws. Consequently, it is an object of this invention to provide a safety interlock which requires all components of the powered surgical saw to be properly assembled before the saw can effectively cut tissue.
It is another object of this invention to provide a sternum saw with a sternum safety guard which necessarily has to be in proper position in order to enable operation of the saw.
It is also an object of this invention to produce a powered surgical saw with a means for attaching the saw blade to the handpiece without using an extra tool. Such a handpiece will be sometimes referred to as a "wrench-less" handpiece.
It is yet another object of this invention to produce, in a powered surgical saw, a safety interlock which simultaneously locks and properly positions a blade and a blade guard.